First results of the bundle test QUENCH-19 with FeCrAl claddings

The QUENCH-19 bundle experiment with FeCrAl(Y) claddings and 4 FeCrAl(Y) spacer grids as well as 8 KANTHAL APM corner rods and KANTHAL APM shroud was conducted at KIT on 29th August 2018. This was performed in cooperation with the Oakridge National Laboratory (ORNL).
The test objective was the comparison of FeCrAl(Y) and ZIRLO™ claddings under similar electrical power and gas flow conditions. In common with the previous QUENCH-15 experiment, the bundle was heated by a series of stepwise increases of electrical power from room temperature to a maximum of ≈600 °C in an atmosphere of flowing argon (3.45 g/s) and superheated steam (3.6 g/s). The bundle was stabilised at this temperature, the electrical power being ≈4 kW. During this time the operation of the various systems was checked.
In a first transient, the electrical power was controlled with the same electrical power history as the QUENCH-15 test. As a result, the bundle was heated to peak cladding temperature of about 1000 °C reached at about 4000 s. It showed a slowed bundle heating than for the QUENCH-15 bundle (1200 °C reached at about 3000 s). In this test phase about 0.3 g of hydrogen were produced (QUENCH-15: 23.3 g).
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In the following phase, the power was increased continuously to 18.12 kW (corresponds to maximal power of the QUENCH-15 test). After reaching of this value the power was kept constant during about 2000 s. At the end of this phase the maximal peak cladding temperature of Tpct≈1500 °C was reached. Much lower heating rate in comparison to QUENCH-15 was measured. Exceeding Tpct≈1400 °C sharp increase of hydrogen release rate was observed.
Then reflood was initiated at ≈9100 s, connected with switching the argon injection to the top of the bundle, first rapidly filling the lower plenum of the test section with 4 kg of water, and continuing by injecting ≈48 g/s of water. The electrical power was reduced to 4.1 kW during the reflood.
A temperature excursion was not observed. The temperatures at all elevations decrease immediately after water injection. The total hydrogen release during the whole test was 9.2 g compared to 47.6 g in the QUENCH-15 test with much shorter high electrical power phase.
The videoscope observation of the bundle at the positions of the withdrawn corner rods showed the damage of several claddings at the bundle elevations between 850 and 1000 mm. The claddings were failed either due to interaction with melted thermocouples (mostly) or by spalling of small annular cladding parts.